Corrosion-resistant greases and wet lubricants

ABSTRACT

A corrosion-resistant wet film lubricant composition includes a lubricating pigment, an oil, and a thickener. The lubricating pigment comprises graphene platelets and is dispersed in the oil, and the thickener thickens the wet film lubricant. The graphene platelets are oxidized and functionalized with a silane. In another example, a method of producing a corrosion-resistant lubricant includes oxidizing exfoliated graphene to produce oxidized graphene platelets, functionalizing the oxidized graphene platelets with a silane to produce functionalized graphene platelets, and dispersing the functionalized graphene platelets in a lubricant composition, wherein the lubricant composition comprises an oil and a thickener.

BACKGROUND

The present disclosure relates to lubricants having improved corrosionresistance, and more particular to wet film lubricants having improvedresistance to galvanic or bimetallic corrosion.

Some wet film lubricants can facilitate galvanic or bimetallic corrosionbetween lubricated components. In particular, wet film lubricants thatinclude graphite can increase the rate of galvanic corrosion.Chromate-based anti-corrosion agents can be added to wet film lubricantsto reduce the rate of galvanic corrosion of metals such as aluminum,copper, cadmium, zinc, magnesium, tin, silver, iron, and their alloys toreduce and slow the rate of galvanic corrosion. Chromate-basedanti-corrosion agents, which contain hexavalent chromium, may pose anumber of environmental and health risks, and for this reason hexavalentchromium is heavily regulated in, for example, the U.S. and the E.U.

SUMMARY

In one example, a corrosion-resistant wet film lubricant compositionincludes a lubricating pigment, an oil, and a thickener. The lubricatingpigment comprises graphene platelets and is dispersed in the oil, andthe thickener thickens the wet film lubricant. The graphene plateletsare oxidized and functionalized with a silane.

In another example, a lubricated article includes a surface and acoating on the surface of a corrosion-resistant wet film lubricantaccording to another example of this disclosure.

In yet a further example, a method of producing a corrosion-resistantlubricant includes oxidizing exfoliated graphene to produce oxidizedgraphene platelets, functionalizing the oxidized graphene platelets witha silane to produce functionalized graphene platelets, and dispersingthe functionalized graphene platelets in a lubricant composition,wherein the lubricant composition comprises an oil and a thickener.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural formula of an example of a graphene plateletfunctionalized with a silane.

FIG. 2 is a schematic drawing of an example of a surface coated with acorrosion-resistant wet film lubricant including a functionalizedgraphene platelet.

FIG. 3 is a structural formula of an example of a silane suitable forfunctionalizing a graphene platelet.

FIG. 4 is a reaction schematic for making an example of a grapheneplatelet functionalized with a silane.

FIG. 5 is flow diagram of an example of a method of producing acorrosion-resistant wet film lubricant including a functionalizedgraphene platelet.

DETAILED DESCRIPTION

The present disclosure includes functionalized graphene platelets andlubricants containing functionalized graphene platelets. Thefunctionalized graphene platelets disclosed herein function asanti-corrosive agents and allow for the preparation of lubricants thatdo not include chromate-based anti-corrosive agents. Further, thefunctionalized graphene platelets disclosed herein function aslubricating pigments.

FIG. 1 is a structural formula of an example of a graphene plateletfunctionalized with a silane. Graphene is a single layer of carbon atomsarranged in a two dimensional and generally hexagonal lattice. Graphiteis composed of many layers of graphene. Graphene can be advantageouslyused as a lubricant pigment due to the ability of individual graphenelayers to slide relative to one another. Graphite, similarly, can beused as a lubricant pigment due to the ability of graphene layers of thegraphite to shear under friction force and slide relative to oneanother.

The graphene platelet depicted in FIG. 1 is an oxidized grapheneplatelet (e.g., a graphene oxide or a reduced graphene oxide) includingoxygen-containing functional groups, such as hydroxyl groups, and isfunctionalized with silane groups via a condensation reaction. As usedherein, “surface oxygen” and “surface oxides” refer to theoxygen-containing functional groups that extend away from a planarsurface of an oxidized graphene platelet and are suitable forfunctionalization with silanes. As is shown in FIG. 1 , the silane formssilyl ether linkages with the graphene platelet. Each silane can formsingle or multiple silyl ether linkages with the graphene platelet. Thesilane can be, for example, an alkoxysilane, such as a monoalkoxy-,dialkoxy-, or trialkoxysilane. Further, the alkoxy group can be selectedbased on steric properties and ability of the alkoxysilane to formlinkages with the graphene platelet. For example, the alkoxysilane canbe a methoxysilane or an ethoxysilane. As will be explained in moredetail, especially with respect to FIGS. 2-3 , the silane also includesa functional group that is selected based on its interaction with otherlubricant components and/or the surface of a lubricated article.

In the depicted example, the graphene platelet is functionalized with(3-glycidyloxypropyl)triethoxysilane. However, the graphene platelet canbe functionalized with other suitable silanes, such as(3-glycidyloxypropyl)trimethoxysilane or(3-aminopropyl)trimethoxysilane. The oxidized graphene can be, forexample, graphene oxide (GO), reduced graphene oxide (rGO), or hydroxygraphene. As used herein, “graphene”, “graphene oxide”, “reducedgraphene oxide,” and “hydroxy graphene” refer to graphene platelets. Thediameter of the graphene platelet can be selected to optimize lubricity.As used herein, the “diameter” of a graphene platelet refers to anaverage diameter of the two-dimensional lattice of the grapheneplatelet. For example, the graphene platelet can have an averagediameter of between 1 and 25 μm. The “thickness” of a graphene plateletrefers to the average width of the graphene platelets in a directionnormal to the lattice of the graphene platelet.

The graphene platelet depicted in FIG. 1 is depicted as a single layerof carbon for illustrative purposes. The graphene platelet can also be,for example, a graphene nanoplatelet (GNP) having multiple graphenelayers. GNPs including multiple layers can be similarly oxidized andfunctionalized to produce functionalized GNPs having advantageouslylubrication and anti-corrosion properties. For example, thefunctionalized GNPs can have an average thickness of between one andtwenty graphene layers, with the exterior layers includingfunctionalized silanes.

Graphite platelets have desirable properties for increasing thelubricity of lubricants, but are conductive and can act as conduits tofacilitate galvanic corrosion. For this reason, graphite-containinglubricants usually contain an additional corrosion inhibitor, such as achromate-based inhibitor or is similarly restricted on certain metals,such as aluminum, as the graphite may induce galvanic corrosion.Graphene platelets also have desirable properties for increasing thelubricity of lubricants and provide improved resistance to galvaniccorrosion as compared to graphite platelets. Advantageously, graphenesinhibit, rather than facilitate, galvanic corrosion. Functionalizedgraphene platelets provide improved dispersion into a lubricant matrixand have reduced agglomeration as compared to unfunctionalizedgraphenes. As such, functionalized graphenes advantageously functionboth to prevent corrosion and to increase lubricity, reducing the needfor chromate-based substances. The functionalized graphenes can be usedas lubricant pigments and allow for the creation of corrosion-resistantlubricants that do not include chromate-based inhibitors. Although thegraphene platelet

FIG. 2 is a schematic drawing of lubricated article 100, which is anexample of a surface coated with a corrosion-resistant wet filmlubricant including a functionalized graphene platelet. Lubricatedarticle includes wet film lubricant 102 and article 104.

Wet film lubricant 102 is a corrosion-resistant wet film lubricant andcoats a surface of article 104. Wet film lubricant 102 includes alubricant pigment, an oil, and a thickener. The lubricating pigmentincludes silane-functionalized graphene platelets to provide lubricityto wet film lubricant 102. The oil facilitates the dispersion of thelubricating pigment and promotes homogeneity of the lubricantcomposition. The thickener functions to thicken the wet film lubricantto an appropriate viscosity and/or consistency.

Article 104 is an article requiring lubrication, such as a fastener, avalve component, a slide, or another part that functions by slidingrelative to a separate structure. Article 104 is formed of a metalmaterial that is susceptible to galvanic corrosion. For example, article104 can be formed from an aluminum material. In operational conditions,article 104 is disposed adjacent to a second metallic component and wetfilm lubricant 102 provides lubricity between article 104 and the secondmetallic component, allowing article 104 and the second metalliccomponent to slide relative to one another.

Existing graphite-based lubricants can facilitate galvanic corrosionbetween, for example, article 104 and the second metallic component orarticle 104 and a component of dry film lubricant 102, requiring anadditional corrosion inhibitor to prevent galvanic corrosion. Asdescribed previously, chromate-based corrosion inhibitors are oftenadded to existing graphite-based lubricants to prevent galvaniccorrosion. Chromate-based compounds may pose a number of environmentaland health risks, and are heavily regulated in, for example, the U.S.and the E.U. Advantageously, the silane-functionalized GNPs in wet filmlubricant 102 both increase lubricity and prevent corrosion without theneed for an additional corrosion inhibitor. As such, in some examples,wet film lubricant 102 does not include a chromate compound and is,therefore, substantially chromate-free.

Although the anti-corrosion properties of silane-functionalized grapheneplatelets have previously been characterized in paint and coatingprimers, the ability of silane-functionalized graphene platelets tofunction both as anti-corrosives and as lubricant pigments was unknown.In particular, at high concentrations, silane functionalized grapheneplatelets can cause the viscosity of a lubricant composition to increasesubstantially, which is undesirable for lubricant function. However,adding functionalized graphene platelets at a relatively lowconcentration in the lubricant composition confers substantialanti-corrosion and lubricity properties to the lubricant compositionwithout substantially increasing the viscosity of the lubricantcomposition. For example, adding functionalized graphene at aconcentration between 0.1 wt % and 0.5 wt % in the lubricant compositionprovides both sufficient lubricity and anti-corrosion properties whilemaintaining acceptable viscosity. In some examples, the resultantlubricant composition has acceptable viscosity with up to 5 wt % offunctionalized graphene platelets. Advantageously, lubricantcompositions that include functionalized graphene at a concentration of0.1 wt %-5 wt % do not require additional lubricant pigments to achievesufficient lubricity and similarly do not require additionalanti-corrosives, such as chromate compounds or other anti-corrosioncompounds, to prevent galvanic corrosion.

As will be described in more detail with respect to FIG. 3 , the silaneused to functionalize the oxidized graphene can further be selected toimprove dispersibility. For example, the silane can be selected toincrease interactions between the functionalized graphene lubricantpigment of wet film lubricant 102 and the surface of article 104, andfurther to decrease interactions between the functionalized lubricantgraphene pigment and other components of the wet film lubricant 102,including adjacent functionalized graphene pigments, allowing forimprove lubricity over conventional graphite lubricant pigments.Notably, unfunctionalized graphenes may exhibit poor dispersion inlubricant compositions. The functionalized graphenes disclosed hereinhave substantially improved dispersion as compared to unfunctionalizedgraphenes, improving the lubricity of lubricant compositions containingthe functionalized graphenes disclosed herein as compared to lubricantcompositions containing only unfunctionalized graphenes. To this extent,lubricant compositions including a functionalized graphene describedherein offer a number of advantages relating to lubricity and galvaniccorrosion over conventional lubricant compositions.

Although additional components that confer lubricity or anti-corrosiveproperties are not required for the function of wet film lubricant 102,wet film lubricant 102 can include additional lubricating and/oranti-corrosive agents in some examples. For example, wet film lubricant102 can also include MoS₂, WS₂, and/or BN to improve lubricity.Similarly, in some examples dry film lubricant 102 can includechromate-based corrosion inhibitors or another suitable corrosioninhibitor, such as magnesium silicate, praseodymium hydroxide, a zincsalt, a rare earth trivalent chromium (RECRO₃) compound, or anothersuitable compound. RECRO₃ compounds include trivalent chromium and atleast one rare earth cation. Example rare earth cations include cerium(Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd),holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd),praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc),terbium (Tb), thulium (Tm), ytterbium (Yb) and yttrium (Y) and thealkaline earth element precursor includes at least one of magnesium(Mg), calcium (Ca), strontium (Sr), and barium (Ba). RECRO₃ compoundsare substantially less toxic than hexavalent chromium-based corrosioninhibitors.

FIG. 3 is a structural formula of an example of a silane suitable forfunctionalizing a graphene platelet. FIG. 3 includes a silicon atomcovalently bonded to three R groups (R₁-R₃) and one X group. R groupsrepresent positions that can be occupied by leaving groups. X representsa position that is not occupied by a leaving group and instead isoccupied by a functional group for affecting the lubricity of afunctionalized graphene platelet. As used herein, “leaving groups” referto functional groups that retain an electron pair following heterolyticbond cleavage between the silicon atom and the leaving group. Theleaving group can be, for example, a weak Lewis base. In some examples,the leaving groups at R₁-R₃ are ethers, such as ethoxy- ormethoxy-moieties, or alcohols. At least one of R₁-R₃ is a leaving groupto facilitate the formation of a covalent bond between the silane and anoxidized graphene platelet. However, the others of R₁-R₃ can benon-leaving groups. For example, one or more of R₁-R₃ can be an alkane,such as methyl- or ethyl-moieties, or a hydrogen. R₁-R₃ can be the sameor different from one another.

X can include one or more an alkane, a haloalkane, a perhaloalkane, anester, an ether, an amide, an amine, and an epoxy. For example, X caninclude an alkane chain, an ether, and an epoxy group. The chemicalcomposition and structure of X is selected to improve lubricity of thefunctionalized graphene. For example, the structure of X can be selectedto improve interlaminar spacing between adjacent functionalized grapheneplatelets in wet lubricant film 102 and improve the ability of adjacentfunctionalized graphene platelets to slide relative to each another. Asa specific example, including a perfluoro group in X can increaseinterlaminar spacing, improving lubricity, as well as impart greaterhydrophobic properties to the lubricant. Advantageously, improving theability of adjacent functionalized graphene platelets to slide relativeto one another improves the lubricity of wet film lubricant 102.

Similarly, the chemical composition and structure of X can be selectedto improve dispersion in wet lubricant film 102. For example, X can beselected based on the chemistry of an oil for a wet film lubricant, suchthat there is an unfavorable interaction between the oil and thefunctionalized graphene that increases the propensity of thefunctionalized graphene to localize adjacent to the surface of article104. As a specific example, X can include a perfluoro group to cause thefunctionalized graphene to repel from other hydrocarbons in wet filmlubricant 102. As a further example, the chemical composition andstructure of X can be selected to improve adhesion between thefunctionalized graphene platelets and article 104, thereby increasingthe propensity of the functionalized graphene platelets to localizeadjacent to the surface of article 104. Advantageously, choosing achemical composition and structure of X that increases the propensity ofthe functionalized graphene to localize adjacent to the surface ofarticle 104 improves the lubricity of wet film lubricant 102.

The identities of R₁-R₃ and X can further be selected based on theirimpact on the efficiency or rate of functionalization of an oxidizedgraphene platelet. For example, one or more of R₁-R₃ and X can beselected based on their steric properties, as sufficiently bulky groupscan inhibit functionalization of oxidized graphene platelets.

FIG. 4 is a reaction schematic for making an example of a grapheneplatelet functionalized with a silane. According to the reactionschematic shown in FIG. 4 , graphite is exfoliated and oxidized to formoxidized graphene. The graphite can be exfoliated using, for example,high-shear mixing, ball milling, sonication, chemical exfoliation, useof exfoliating surfactants, or a combination of the foregoingtechniques, among other options. High-shear mixing can also be used toenhance dispersion of the graphene platelets in solution. In someexamples, exfoliation and oxidation occurs substantially simultaneously.For example, exfoliation can be performed in oxidizing conditions, suchas via a chemical exfoliation technique, to produce exfoliated andoxidized graphene. Chemical reduction of the graphene can be performedto reduce the number of surface oxides produced by oxidation.

Following exfoliation and oxidation, the oxidized graphene is silanizedto yield functionalized graphene. The oxidized graphene is silanized bya condensation reaction between a silane and a surface oxygen of theoxidized graphene, yielding a functionalized graphene and a free leavinggroup. The silane is one having the chemical formula describedpreviously with respect to FIG. 3 . As at least one of R₁-R₃ of thestructural formula shown in FIG. 3 is a leaving group, at least one ofR₁-R₃ is covalently bonded to a graphene platelet.

The silanization reaction can be conducted by first dispersing grapheneplatelets in a reaction solvent. The concentration of graphene plateletsin the solvent can be 10-30 wt % of the reaction. The reaction solventcan be, for example, a polar solvent. In some examples, the polarsolvent can be an alcohol, such as ethanol. In some examples, thesilanes functionalize up to 15 wt % of surface oxygen of the oxidizedgraphene platelets.

Although the disclosures herein refer generally to functionalizinggraphene platelets with silanes, other suitable compounds can be used tofunctionalize graphenes to reduce corrosion and/or improve lubricity. Inthese examples, the reaction schematic shown in FIG. 4 can be modifiedto include an alternative reaction step to functionalize the oxidizedgraphene in place of the depicted silanization reaction.

FIG. 5 is flow diagram of method 500, which is an example of a method ofproducing a corrosion-resistant wet film lubricant including afunctionalized graphene platelet. Method 500 includes steps of oxidizingexfoliated graphene platelets (step 502), functionalizing the oxidizedgraphene platelets (step 504), and dispersing the functionalizedgraphene platelets in a lubricant composition (step 506).

Oxidizing the exfoliated graphene platelets (step 502) andfunctionalizing the oxidized graphene platelets (step 504) can beperformed in substantially the same manner as described previously withrespect to the reaction schematic of FIG. 4 . In step 506, thefunctionalized graphene platelets are dispersed in a lubricantcomposition, such as wet film lubricant 102. The functionalized grapheneplatelets are added to an oil and a thickener to create a lubricantcomposition. The functionalized graphene platelets are dispersed in thelubricant composition by sonication, high-shear mixing, or anothersuitable method to create a homogeneous mixture. The resultant lubricantcomposition is a corrosion-resistant lubricant composition.

As described previously, at high concentrations, the functionalizedgraphene platelets can cause the viscosity of the lubricant compositionto increase substantially, which is undesirable for lubricant function.However, adding functionalized graphene platelets at a relatively lowconcentration in the lubricant composition, such as 0.1 wt % and 0.5 wt%, confers substantial anti-corrosion and lubricity properties to thelubricant composition without substantially increasing the viscosity ofthe lubricant composition. In some examples, the resultant lubricantcomposition has acceptable viscosity with up to 5 wt % of functionalizedgraphene platelets.

Advantageously, lubricant compositions that include a functionalizedgraphene platelet described herein at a concentration of 0.1 wt %— 5 wt% do not require additional lubricant pigments to achieve sufficientlubricity and similarly do not require additional anti-corrosives toprevent galvanic corrosion. To this extent, lubricant compositions thatinclude a functionalized graphene described herein do not require, forexample, a chromate-based corrosion inhibitor and are, therefore,substantially chromate-free. Further, the functionalized grapheneplatelets described herein offer improved lubricity over conventionalgraphite and graphene lubricant pigments.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

An embodiment a corrosion-resistant wet film lubricant compositionincludes a lubricating pigment, an oil, and a thickener. The lubricatingpigment comprises graphene platelets and is dispersed in the oil, andthe thickener thickens the wet film lubricant. The graphene plateletsare oxidized and functionalized with a silane.

The corrosion-resistant wet film lubricant composition of the precedingparagraph can optionally include, additionally and/or alternatively, anyone or more of the following features, configurations and/or additionalcomponents:

A corrosion-resistant wet film lubricant composition according to anexemplary embodiment of this disclosure includes, among other possiblethings, a lubricating pigment, an oil, and a thickener. The lubricatingpigment comprises graphene platelets and is dispersed in the in the oil,and the thickener thickens the wet film lubricant. The grapheneplatelets are oxidized and functionalized with a silane.

A further embodiment of the foregoing corrosion-resistant wet filmlubricant, wherein the graphene platelets have a concentration of 0.1 wt% to 0.5 wt % in the lubricant composition.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the silane forms at least one silyl etherlinkage with the graphene platelets.

A further embodiment of any of the foregoing corrosion-resistant dryfilm lubricants, wherein the silane comprises an alkoxysilane.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the silane is selected from a group consistingof a monoalkoxysilane, a dialkoxysilane, and a trialkoxysilane.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the silane is selected to increase thepropensity of the graphene platelets to localize adjacent to a surfaceof an article.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the wet film lubricant composition does notinclude chromate.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the graphene platelets are graphenenanoplatelets.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the graphene nanoplatelets have averagediameters between 1 micrometer and 25 micrometers.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the silanes functionalize up to 15 wt % ofoxygen of the graphene platelets.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the graphene platelets have a concentration ofless than 5 wt % in the lubricant composition.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the silane is selected to improve lubricity.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the wet film lubricant composition does notinclude chromate.

The graphene platelets have average diameters between 1 micrometer and25 micrometers.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein the silane is represented by the followingformula:

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein R₁ is selected from a group consisting ofethers and alcohols.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein R₂ is selected from a group consisting ofalcohols, ethers, alkanes, and hydrogen.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein R₃ is selected from a group consisting ofalcohols, ethers, alkanes, and hydrogen.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein X includes one or more of an alkane, ahaloalkane, a perhaloalkane, an ester, an ether, an amide, an amine, andan epoxy.

A further embodiment of any of the foregoing corrosion-resistant wetfilm lubricants, wherein at least one of R₁, R₂, and R₃ is covalentlybonded to the graphene platelets.

An embodiment of a lubricated article includes a surface and acorrosion-resistant wet film lubricant. The coating of thecorrosion-resistant dry lubricant is on the surface.

The lubricated article of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

A lubricated article according to an exemplary embodiment of thisdisclosure includes, among other possible things, a surface and acorrosion-resistant wet film lubricant according to another embodimentof this disclosure. The coating of the corrosion-resistant dry lubricantis on the surface.

A further embodiment of the foregoing lubricated article, wherein thesurface comprises an aluminum material.

An embodiment of a method of producing a corrosion-resistant lubricantincludes oxidizing exfoliated graphene to produce oxidized grapheneplatelets, functionalizing the oxidized graphene platelets with a silaneto produce functionalized graphene platelets, and dispersing thefunctionalized graphene platelets in a lubricant composition, whereinthe lubricant composition comprises an oil and a thickener.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

A method of producing a corrosion-resistant lubricant includes accordingto an exemplary embodiment of this disclosure includes, among otherpossible things, oxidizing exfoliated graphene to produce oxidizedgraphene platelets, functionalizing the oxidized graphene platelets witha silane to produce functionalized graphene platelets, and dispersingthe functionalized graphene platelets in a lubricant composition,wherein the lubricant composition comprises an oil and a thickener.

A further embodiment of the foregoing method, wherein functionalizingthe oxidized graphene platelets with a silane comprises functionalizingup to 15 wt % of oxygen of the oxidized graphene platelets.

A further embodiment of any of the foregoing methods, wherein dispersingthe functionalized platelets in the lubricant composition comprisesadding the functionalized graphene platelets at a concentration of 0.1wt % to 0.5 wt % in the lubricant composition.

A further embodiment of any of the foregoing methods, wherein the silaneforms at least one silyl ether linkage with the oxidized grapheneplatelets.

A further embodiment of any of the foregoing methods, wherein the silaneis selected from a group consisting of a monoalkoxysilane, adialkoxysilane, and a trialkoxysilane.

A further embodiment of any of the foregoing methods, wherein the silaneis represented by the following formula:

A further embodiment of any of the foregoing methods, wherein R₁ isselected from a group consisting of ethers and alcohols.

A further embodiment of any of the foregoing methods, wherein R₂ isselected from a group consisting of alcohols, ethers, alkanes, andhydrogen.

A further embodiment of any of the foregoing methods, wherein R₃ isselected from a group consisting of alcohols, ethers, alkanes, andhydrogen.

A further embodiment of any of the foregoing methods, wherein X includesone or more of an alkane, a haloalkane, a perhaloalkane, an ester, anether, an amide, an amine, and an epoxy.

A further embodiment of any of the foregoing methods, wherein at leastone of R₁, R₂, and R₃ is covalently bonded to the graphene platelets.

A further embodiment of any of the foregoing methods, wherein the silaneis selected to increase the propensity of the functionalized grapheneplatelets to localize adjacent to a surface of an article.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A corrosion-resistant wet film lubricant composition comprising: alubricating pigment comprising graphene platelets, wherein the grapheneplatelets are partially oxidized and functionalized with a silane; anoil, wherein the lubricating pigment is dispersed in the oil; and athickener for thickening the wet film lubricant; and wherein: the silaneis selected to increase the propensity of the oxidized andfunctionalized graphene platelets to localize adjacent to a surface ofan article, the article comprising a metal material; the silane isselected to reduce galvanic corrosion of the article; up to 15 wt % ofoxygen of the oxidized graphene platelets are functionalized; and thesilane is represented by the following formula:

wherein: R₁ is selected from a group consisting of ethers and alcohols;R₂ is selected from a group consisting of alcohols, ethers, alkanes, andhydrogen; R₃ is selected from a group consisting of alcohols, ethers,alkanes, and hydrogen; X includes one or more of an alkane, ahaloalkane, a perhaloalkane, an ester, an ether, an amide, an amine, andan epoxy; and at least one of R₁, R₂, and R₃ is covalently bonded to theoxidized graphene platelets.
 2. (canceled)
 3. The corrosion-resistantwet film lubricant composition of claim 1, wherein the oxidized andfunctionalized graphene platelets have a concentration of 0.1 wt % to 5wt % in the lubricant composition.
 4. The corrosion-resistant wet filmlubricant composition of claim 1, wherein the silane forms at least onesilyl ether linkage with the oxidized graphene platelets.
 5. Thecorrosion-resistant wet film lubricant composition of claim 1, whereinthe silane comprises an alkoxysilane.
 6. The corrosion-resistant wetfilm lubricant composition of claim 1, where in the silane is selectedfrom a group consisting of a monoalkoxysilane, a dialkoxysilane, and atrialkoxysilane. 7-8. (canceled)
 9. The corrosion-resistant wet filmlubricant composition of claim 1, wherein the wet film lubricantcomposition does not include chromate.
 10. The corrosion resistant wetfilm lubricant composition of claim 1, further comprising an additionalcorrosion inhibitor.
 11. The corrosion-resistant wet film lubricantcomposition of claim 1, wherein the graphene platelets have averagediameters between 1 micrometer and 25 micrometers.
 12. Thecorrosion-resistant wet film lubricant composition of claim 1, wherein:the oxidized and functionalized graphene platelets have a concentrationof less than 5 wt % in the lubricant composition; the silane is selectedto improve lubricity of the wet film lubricant composition; the wet filmlubricant composition does not include chromate; and the grapheneplatelets have average diameters between 1 micrometer and 25micrometers.
 13. A lubricated article comprising: a surface; a coatingof the corrosion-resistant wet film lubricant composition of claim 1 onthe surface.
 14. A method of producing a corrosion-resistant lubricant,the method comprising: oxidizing exfoliated graphene to produce oxidizedgraphene platelets; functionalizing the oxidized graphene platelets witha silane to produce functionalized graphene platelets; and dispersingthe functionalized platelets in a lubricant composition, wherein thelubricant composition comprises an oil and a thickener; wherein: thesilane is selected to increase the propensity of the oxidized andfunctionalized graphene platelets to localize adjacent to a surface ofan article, the article comprising a metal material; the silane isselected to reduce galvanic corrosion of the article; up to 15 wt % ofoxygen of the oxidized graphene platelets are functionalized; and thesilane is represented by the following formula:

wherein: R₁ is selected from a group consisting of ethers and alcohols;R₂ is selected from a group consisting of alcohols, ethers, alkanes, andhydrogen; R₃ is selected from a group consisting of alcohols, ethers,alkanes, and hydrogen; X includes one or more of an alkane, ahaloalkane, a perhaloalkane, an ester, an ether, an amide, an amine, andan epoxy; and at least one of R₁, R₂, and R₃ is covalently bonded to theoxidized graphene platelets.
 15. (canceled)
 16. The method of claim 14,wherein dispersing the functionalized platelets in the lubricantcomposition comprises adding the functionalized graphene platelets at aconcentration of 0.1 wt % to 0.5 wt % in the lubricant composition. 17.The method of claim 14, wherein the silane forms at least one silylether linkage with the graphene platelets.
 18. The method of claim 14,where in the silane is selected from a group consisting of amonoalkoxysilane, a dialkoxysilane, and a trialkoxysilane. 19-20.(canceled)